Hi,
I'm having some trouble with the front left brake piston. It seems that it does not return fully after braking. I changed the brake discs and pads last week and found that the left hand side pads were worn to the metal shoe and the disc was badly grooved, whereas the right hand side pads were only half way worn.
While changing the pads, I had to let off the bleed screw to push the piston back in, to allow the calliper close over the new pads and disc.
While driving after the change, I noticed a smell of burning brakes and the car is pulling to the left.
So I'm fairly sure the left hand side piston is not returning after braking and is holding the pad, admittedly lightly as there is only a slight pull to the left, against the disc.
My question is are the brake callipers servicable? As in, is it possible to dismantle and clean them, blow out the lines with compressed air to remove blockages, and reassemble them?
Would I need a replacement set of seals?
Any help is greatly appreciated as my car is off the road at the moment as a result and I'd like to have it back working as soon as possible.

yes yes and yes.

You need to take it apart. Get the piston out. Clean up everything and new seals on it all!
Or new caliper

It may not be the caliper. The flexible brake hose to the caliper can shed its lining and act as a kind of one way valve holding the pressure on the piston. I suppose you've checked the caliper giude pins. I've had trouble before with the pads sticking in the caliper and wearing unevenly. Needed to clean all the crud from the caliper and put some copper grease in the right places.

Take out the brake pads and CAREFULLY pump out the piston but not too far. Dont run the engine and dont let the brake fluid level go too low. If the piston is rusty you need a rebuild with new piston and new seals. Its probably as cheap to get a new caliper. Try www.brakeparts.co.uk/

Push the piston back slowly with a G clamp or suitable lever. If it comes out easily enough but wont go back the flexy hose might be suspect. If it will only go back with the bleed nipple open its deffo the brake hose.

If one side is dodgy the other side might not be far behind so check that too. If thje calipers are replaced fit new hoses as well.